Sound recording method and system



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April 7, 1942- w. v. woLFE SOUND RECORDING METHOD AND SYSTEM Filed Dec.29, 1959 3 Sheets-Sheet 5 f c c Patented Apr. 7, 1942 SOUND RECORDINGMETHOD AND SYSTEM Wallace V. Wolfe, Beverly Bills, Calif., assigner toRadio Corporation o! America, a corporation of Delaware ApplicationDecember 2s, 1939, serial No. 311,518 19 claims; (ci. 11s-100.3)

This invention relates to apparatus and methods used in the art ofmotion picture production and particularly to that part of motionpicture production which is concerned with the recording and rerecordingof sound concomitant with the picture.

It is well known in theart that motion pictures are made in a series oftakes or sequences, the sound portion which nally accompanies thevarious sequences being rerecorded from several sources made eitherprior to or at the time of the taking or the pictures. The usualprocedure is to make a picture sequence and simultaneously therewithmake a synchronized sound sequence which will be composed of thedialogue, if any, occurring in the scene. Where certain picturesequences are silent, sound in some form of a musical selection may be.added to form a background for the action. Music may also be added toform a background for dialogue occurring in certain scenes. In manycases, sound eiects, such as hoofbeats, crowd noises, thunder. and thelike, may be added to sequences with and without dialogue. Thesebackground sound eiects are generally taken from pre-recorded soundtracks and are mixed yto make a nal negative `from which will be printedthe combinationpicture and sound lm suitable for theatre use.

The above procedure is known as rerecording, and is sometimes referredto as duping7 and dubbing." Each individual sound track sequence, suchas the dialogue, the background music, hoofbeats, etc., are joinedtogether into respective reels or in the form of individual continuousloops which are then run simultaneously through separate reproducers orsoundheads. The output of each soundhead is combined in a commoncircuit, monitored and recorded during the synchronous projection of areel of the related picture sequences. An operator known as the mixerhas in front vof him on a panel a volume control for each of the soundreproducers. There may be one or more of these operators especiallywhere several sound tracks are being combined. These mixers introducethe particular sound eiect at the proper point and control the volume ofeach sound to obtain the proper coordination and dramatic effect. Nomatter how skilled the mixer, it is necessary to rehearse. and usuallythe greater the number of sound tracks being combined, the larger thenumber of rehearsals. A rehearsal consists of reproducing the relatedsound track during the .simultaneous projection ofthe picturey andvarying the volume controls to obtain the best combination andcoordination of the various sounds as indicated on a loudspeakermonitor' system.

After the rehearsals have been made and the mixer and, perhaps, thedirector, who may be present, are satisfied that the last rehearsal willproduce the desired combination effects, a .sound recorder is connectedto the common output circuit from the mixing panel, and the mixer attempts to repeat the last rehearsal while the sounds are recorded.However, as each rerecording rehearsal generally extends over the lengthof a reel, which isin the neighborhood of a thousand feet of lm, itbecomes extremely difllcult to obtain an exact duplication of the lastrehearsal. In most instances several portions of the final sound takemay not compare in quality with that obtained during one or more of therehearsals. Thus, it is either necessary to repeat the entire reel tocorrect or improve these poor portions of the sound recording and makean entire new recording with the attendant chances of other errors, orlet the sound track go out with a quality below that which is possible.The present invention, therefore, is directed to a rerecording soundsystem wherein a special form of record of each rehearsal is recorded ona medium which will automatically and exactly reproduce all or anydesired portion of a prior rehearsal while permitting the mixer tocorrect or alter all or any portion thereof during the process. That is,each rehearsal record is re' corded on a medium from which reproductionmay be made immediately and during which the same record may bererecorded on the same medium with corrected variations. After rehearsalis completed, the iinal take becomes completely automatic. Thus, as thevarious portions become perfected, they are exactly repeatable so thatonly the best combinations of sound eilects are obtained on the iinalnegative. The system thus saves lm and time, and, most important of all,insures a higher'quality final sound track.

The principal'object of the invention, therefore, is to improve themethods of rerecording film sound tracks.

Another object of the invention is to record a form of control soundtrack during rerecording rehearsals which may be immediately reproducedfor control of a subsequent rehearsal and which may be varied during thesubsequent rehearsal.

A further object of -the invention is to duplicate the variations madeinthe transmission of electrical currents and to enable changes to bemade during the duplication and retransmission of the currents.

A further obiect of the invention is to record the control variationmade in a rerecording channel during a rehearsal and reproduce, eraseand rerecord the control variations. during a subsequent rehearsal.

A further object of the invention is to enable the best or any desiredportions of a number of rerecording rehearsals to be duplicated orchanged during the production of the ilnal record.

Although the novel features which are believed to be characteristic ofthis invention will be pointed out with particularity in the claimsappended herewith. the invention itself, its objects and advantages, themanner of its organization and the mode of its operation will be betterunderstood by referring to the following description read in conjunctionwith the accompanying drawings forming a part thereof, in which- Figurel is a diagrammatic arrangement of a single rerecording channelembodying the invention:

Figure 2 is a diagrammatic circuit arrangement of two rerecordingchannels embodying the invention; and

Figure 3 is a diagrammatic circuit arrangement of two rerecordingchannels embodying a modification of the invention.

Referring now to Fig. l, a sound reproducing system usually referred toas a soundhead is represented by a light source 5, lenses l and 1, and aphotocell C. These elements are adapted in translate the sound track ona iilm l supplied from a reel Il and taken up by a reel Il. 'I'he film lis advanced past the translation point by a drive sprocket il driven bya motor Il. The variations in light impressed upon thel photoelectriccell l are translated into electrical currents which are fed into avariable gain ampliner Il. The output of this amplifier is impressedupon a standard ampliiier i1 feeding a standard recorder Il of any wellknown type. For the purpose of monitoring rehearsals and the finalrecording. a portion of the output of an amplifier i'l is impressed uponan amplifier 2l feeding a loudspeaker 2|.

In the usual rerecording system, a gain control is associated with thestandard amplifier for varying the' amplitude of the transmittedcurrents in accordance with the mixers idea of what the proper soundlevel should be for the picture action. In the present system thesevariations in amplitude are accomplished in a different manner. A mixerpanel shown at 2l contains a potentiometer, rheostat or resistance padas indicated which will vary the amplitude of a constant frequency tonesupplied trom an oscillator 2l through a switch 21 when the latter is inits left-hand position. The tone is rectined in a rectifier 2s and thedirect current is applied to the control grid or grids of the tubes ofthe variable gain amplliler It which preferably employs variable mutubes to provide a straightline variable gain characteristic. Thus. thepresent system employs an intermediate or secondary current source whichis varied and which.

in turn. controls the amplitude of the currents in the rerecordingchannel.

In addition to the use of a secondary control current, the presentsystem employs means for recording and reproducing the secondary currentas modined by the mixer. This means is a magnetic wire recording systemhaving a recording element Il connected through a switch Il intermediatethe mixer panel 2l and rectifier Il. Reproduction from the wire Il isobtained from a pickup element 3l over conductors 34 through switch 21when the latter is in its right-hand position. The record on the wiremay be erased by an erasing element 3l under a control 30 positioned atthe control mixing panel 2l. The lmagnetic wire recorder comprises atakeup reel 31 and a supply reel ll for the wire 39. and a driving motor40 and a footage marker Il of any satisfactory type. The motor is undercontrol of the mixer at l2. In operating the above system the soundheadmotor I4 and ythe magnetic wire recorder motor I0 are synchronized andthe wire is driven at the proper relative speed to maintain synchronismbetween the sound tracks at all times. The wire may be advancedsynchronously by running it between driving rollers with a separatetakeup reel or it may be in the form of a tape with sprocket holestherein. It may also be run at a relatively slower speed than theregular illm reproducer and recorder.

When the ilrst rehearsal is made, the switch 3| is closed and switch 21is to the left, connecting oscillator 28 to panel 25. As the mixeroperator varies the amplitude of the constant frequency tone fromoscillator 28, and thereby varies the gain of the amplifier It to changethe amplitude of the signal as indicated in the loudspeaker Il, a recordof the constant frequency tone with its varying amplitude is made on thewire l! traveling to the left as indicated by the arrow on the reel l1.A certain start mark is made on the wire 3l at the beginning of therehearsal and when the wire is rewound on reel 3l, the mark is set atpickup 33 instead of pickup Il for the second run. For the second run orrehearsal, switch 21 is thrown to the right, connecting pickup Il withthe mixing panel 2l. Switch 3| may or may not be opened, as will beexplained hereinafter. Should certain portions of the first rehearsal beconsidered satisfactory. the tone from the pickup 33 will automaticallycontrol the gain of amplifier Il according to the first rehearsal, themixer keeping his dial fixed in position at panel 25. During thisprocedure the mixer may have switch 3l open and the eraser controlinactive. If the switch Il is closed and the eraser control is active,then the same variations being reproduced may be rerecordedsimultaneously.

During the reproduction, the mixer may change or vary certain portionsof the first rehearsal, these changes being rerecorded at ll. It is thusobvious that the new record made by recording element 30 may be acombination of the rst volume variations which are erased at Il andrerecorded at 30, plus any modlncations made therein by the operator byadjusting his dial on panel 25. In this manner, the best variations inthe sound obtained during a rehearsal are retained and are alwaysrepeatable without their being subject to human error. Thus, to make thefinal negative, it is only necessary to permit the pickup J3 to controlthe rectiiler 2l without any attention from the mixer, his control dialremaining iixed. It should be obvious, therefore. that only one film isrequired for the final recording, that the time required for rerecordingis shortened, and that a better quality record is obtained.

Referring now to Fig. 2, in which a multiple channel rerecording systemis disclosed, the rst channel comprises a soundhead 50 with its mo-:,avaois tor Il. a variable gain amplifier 52, a standard amplifier 33,and an individual monitoring circuit including an amplifier 04 andloudspeaker l0 with a control switch 56. vA recorder 59 is alsoconnected in the circuit for operation when the negative is to `be made.The second channel is similar to the first and is composed of asoundployed, while the individual monitoring circuits.

may or' may not be used. There are occasions, however, when theseindividual monitors m-ay be used to advantage and, when so desired, maybe simply connected by the switches 56 and 65.

Similarly to the circuit of Fig. 1. the variable gain amplifier 52 iscontrolled by a rectifier 10, while variable gain amplifier 6| iscontrolled by a rectifier 1|. The input of each rectifier is connectedto a mixing panel 13 having respective dials 14 and 15 for respectivechannels. Each rectifier is connectable to a separate oscillator of adifferent frequency, oscillator 1.1 being connected through a switch 18,when in its lefthand position, to rectier 1|, and oscillator 19 beingconnected to rectifier through switch 8| when in its left-hand position.The magnetic wire recording system is of the exact type shown in Fig. 1,and identical elements thereof have been given like numbers.

In the present system the constant frequency tones are applied to thesame recording element 30, and although the frequencies have anon-harmonic relationship to decrease interference therebetween,bandpass filters 83 and 84 are used in the recording circuits controlledby respective switches 85 and 86 to aid in their segregation. 'I'heoutput of the pickup element 33 is also connected to bandpass filters 88and 89 for the same purpose. The system of Fig. 2 operates basically inthe same manner as the system of Fig. 1 except that the mixer nowcontrols the ,two dials 14 and 15 during the rehearsal and there arethus recorded on the wire 39 two constant frequency control signals eachvarying in amplitude according to the manipulation of the respectivedials. When repeating a rehearsal, the switches 18 and 8| are thrown tothe right. In the operation of this multiple channel system, the erasercontrol functions in the same manner as in Fig. l, and with iteffective, and switches 85 and 86 closed, the signal is rerecorded backon the wire 39. In the process, fixed positions of dials 14 and 15 willexactly duplicate the prior changes made in the channels, While changesmay be made in one or both of the channels by adjusting the dials as wasdone during the prior run. Thus, a plurality of' rerecording channelsmay be automatically controlled in the manner shown in Fig. 2,additional channels requiring additional oscillators and filters. Thewire recorder in this instance may be of the wide tape type wherein tworecording elements record along parallel portions of the tape.

Referring now to Fig. 3, another method of recording, reproducing andrerecording the control tones for -a plurality of rerecording channelsis shown, the main distinction between Figs. 2 and 3 being that only oneoscillator is required for all channels in Fig. 3, but a magneticrecording system for each channel is necessary. In

Fig. 3, thel elements of the rerecording channels are omitted since theyare the same as in Fig. 2,

while the elements common to Fiss. 2 and 3 have been given identicalnumbers. Thus, rectifiers 13 and 1| are shown connected to mixer panel13 with its respective dials 14 and 15. In this modication, a singleoscillator 9| is connected to the mixing panel 13 over channel switches92 and 93 so that either rectier 10 or 1| may be connected to theoscillator, or the respective rectiiiers may be connected to their'respective magnetic wire pickups 91 and |04. The channel controlled byrectier 10 has the variations of the control tone impressed over aswitch 95, when closed, on a recording element 96 of a magnetic wirerecorder having the pickup element 91, a wire 98 and an eraser element99 with its control |00. The channel under control of rectifier 1| hasits control tone recorded, when switch |02 is closed, by recordingelement |03 of a magnetic wire recording system having the pickupelement |04, a wire |05, and an eraser element |06 under control of themixer at |01. The pickup element 91 is connected to switch 93 overconductors |08, while pickup element |04 is connected to switch 92 overconductors |09.

The operation of the system of Fig. 3 is substantially the same as thatof Fig. 2 except that the equipment required in Fig. 2 is an oscillatorand respective bandpass filters for each channel and a common magneticrecorder, while the system of Fig. 3 requires only one oscillator iorall channels, no bandpass filters, but a magnetic wire recorder for eachchannel. Each of the magnetic wire recorders has the necessary motordrives, footage controls, etc., as shown in Fig. l, and which are wellknown in the art. In each case, however, reproduction, removal of therecording, and rerecording of the control tone occur simultaneously,during which time variations may be made by the mixer to correct orimprove certain parts of the sound record. In each case, also, whenit isdesired to make a nal take, each channel is controlled automatically bythe recorded control tone. 'I'he start marks placed at recordingelements 96 and |03 when recording enable the wires to be reset atreproducing elements 91 and |04, respectively, when reproducing. Eachrehearsal requires a new start mark, the distance between marks beingequal to the distance between the recording and reproducing elements.Instead of two complete magnetic wire systems, a single wide-tape systemmay be used having plural recording and reproducing elements. In all ofthe systems, amplifiers may be used between the pickup elements and themixing panels to obtain any desired level of the reproduced controltone.

Referring again to Fig. 3 there is shown connected to recording element96 and pickup element 91, by dotted lines, a disc recorder andreproducer of the so-called instantaneous or immediate playback typepreferably employing socalled acetate blanks. The recorder includes adriving motor for rotating a table ||2 upon which is a blank ||3. Thecutter itself is shown at |I4 mounted on the lead screw ||5 in theassembly ||6. The reproducer includes a motor |20 driving turntable |-2|upon which the cut record |22 is placed. The pickup element is of theusual type mounted on the arm |23.

These disc recorder and reproducer units may be substituted for thevarious magnetic wire recorders shown in the different figures. In usingthis modification, however, it is necessary that as soon as the recordis cut on the recorder it be removed and placed on the reproducer and anew blank positioned on the recorder. 4As subsequent rehearsals aremade, the .output of the reproducer will control the gain ofthere-recording channel in the same manner as described above. Changes mayalso be made in the course of the rehearsals. which will be recorded ona new disc. When the iinal take is to be made, it is only necessary toplace the latest cut disc on the reproducer and permit the system tofunction automatically. Start marks are, of course, employed on the discrecords. as it is well known in the motion picture soundondisc art,while the usual synchronizing system vfor driving the motors atsynchronous speed may be employed. It is also to be understood that theuse of film recorders and reproduoers could be used but without theadvantages of the above-described preferred systems.

With the above-described systems, therefore, the best combination ofdialogue, music backgrounds and sound effects derived during a rehearsalare always repeatable without reliance upon human memory or ability.This results in a higher quality iinal product than heretoforeobtainable. A saving is also made in material and time of producing theilnal combination negative for printing to the picture nlm. Recording ofthe currents in the channels themselves on the magnetic wire recordersor on the discs is possible but not recommended because the complexnature of the channel currents requires high quality equipment. Thereproduced quality of a control tone such as a constant frequency frommagnetic wire apparatus is very satisfactory, however, for'controlpurposes.

Although only two rerecording channels have been shown and described asillustrations, it is to be understood that more than two channels may besimultaneously controlled in a similar manner.

I claim as my invention:

l. In sound apparatus. the combination of a source of currentscorresponding to sound waves, a transmission circuit for said currents.a variable gain ampliner for varying the amplitude of said currents insaid circuit, means for generating a secondary current, means forvarying the amplitude of said secondary current by impressing theproducts of rectification of said secondary current on said variablegain amplifier for varying the amplitude of said sound wave currents,independent means for recording only said secondary current, and meansfor reproducing only said secondary current to control the amplitude ofsaid sound wave currents during a subsequent transmission of said soundwave currents over said transmission circuit.

2. Sound apparatus in accordance with claim 1 in which said recordingand reproducing means function simultaneously to rerecord variations inthe secondary current while said original secondary currentautomatically controlling the variation of said sound wave currents.

3. The method of obtaining the repetition of variations made in thetransmission of electrical currents comprising making an individualrecord of the variations made during the transmission oi' said currents,utilizing said record for controlling the re-transmission of saidcurrents. and making a second transmission record of said first recordof transmission variations, said second record including variations madein the transmission of said currents during said re-transmission ci saidcurrents.

4. The method of obtaining the repetition of the variable transmissionof manually varied sound wave currents comprising recording the manualvariations made during the transmission of said currents. controllingthe re-transmission yof said currents by the reproduction of the recorded manual variations, and rerecording the reproduction of theoriginal recorded manual variations together with subsequent manualvariations made during the re-transmission of said currents.

5. Sound apparatus comprising a source of sound wave currents, atransmission circuit for said currents, a secondary source of current.means for varying the amplitude of said secondary current, means forconnecting said source of secondary current to said transmission circuitfor varying the amplitude of said sound wave currents in accordance withthe variations of said secondary current, means for recording saidsecondary current, means for reproducing said secondary current, andmeans for connecting said reproducing means to said connecting meansbetween said source of secondary current and said transmission circuitlsaid recording means being adapted to rerecord said secondary currentduring the reproduction thereof by said reproducing means.

6. Sound apparatus in accordance with claim 5 in which said recordingand reproducing means includes a magnetic wire recorder and reproducerhaving separate recording and reproducing elements, said elements beingadapted to function simultaneously {for recording said reproducedsecondary current.

'1. Sound apparatus in accordance'with claim 5 in which said recordingand reproducing means includes an instantaneous disc recorder andreproducer.

8. 'Ihe method of rerecording sound comprising reproducing a soundrecord, varying the amplitude of the reproduction of said sound record,recording the variations made in the amplitude of said reproduction,reproducing said recorded variations for controlling the re-reproductionof said sound record, and simultaneously rerecording said reproducedvariations as originally recorded and as varied during there-reproduction of said sound record.

9. In a rerecording system, the combination of a soundhead, atransmission circuit for said soundhead, a variable gain amplifier insaid transmission circuit, a rectifier connected to said variable gainamplifier,` means for supplying a constant frequency current to saidrectiner. volume control means for said constant frequency current;means for recording said constant frequency current, means forreproducing said constant frequency current, and means for connectingsaid reproducing means to said rectifier.

10. In a rerecording system, the combination of a plurality ofsoundheads, an individual transmission circuit for each soundhead, avariable gain ampliner in each transmission circuit, a rectier connectedto each variable gain ampliiler, means for supplying a constantfrequency current to each of said rectiilers, volume control means forsaid constant frequency current, means for recording said constantfrequency current, means for reproducing said constant frequencycurrent, and means for connecting said reproducing means to said volumecontrol means.

1l. A rerecording system in accordance with claim 10 in which saidconstant frequency supply means is an oscillator, and` means areprovided for selectively connecting said oscillator and said `andreproducer.

13. A rerecording system in accordance with claim 10 in which saidconstant frequency supply means comprises a single oscillator for saidplurality of rectiers, and said recording and reproducing meanscomprises an individual magnetic wire recorder and reproducer for eachof.

said rectifiers.

14. In a rerecording system having a, fader in-Y volving a movablemanually operable control member adapted to control the amplitude of anelectrical sound current, means for automatically repeating thevariations in amplitude produced in said sound current by said fadercomprising an ampliiler, means for producing a current proportional tothe manual movements of said fader,

means foryarying the gain of said ampliiier by said movement current,means for recording said movement current, and means for reproducingsaid movement current for impression on said amplifier.

15. A system in accordance with claim 14 in which said movement currentis recorded as re- Y produced, said fader varying said current as re'-corded. I

16. A rerecording system comprising a transmission circuit, an amplifierin said circuit, a source of current, manual control means for varyingthe amplitude of said current, means for impressing said current on saidamplifier for varying the gain thereof, a recorder, means forsimultaneously impressing said current on a recorder, and means forreimpressing said current when reproduced'y on said amplifier forvarying the gain thereof in the same manner as when said current was.recorded. I 1'1. A rerecording system in accordance with claim 16 inwhich said reproduced current is rerecorded, said manual control meansbeing adapted to vary the amplitude thereof as rerecorded. 18.' Themethod of rerecording comprising producing anelectrical sound currentfrom an original sound record, audibly reproducing said sound current,manually eilecting desired amplitude modications in said sound currentby reference to such audible reproduction, making a record of suchamplitude modifications, producing an electrical sound current from saidoriginal sound record, repeating the same amplitude modications in saidelectrical sound current under the control of said amplitudemodification record, and making a new record of such amplitudemodifications variedby any additional manual variations made during therepetition.

. 19. The method of obtaining 'a control record for varying theamplitude of transmission of a signal current comprising audiblyreproducing n said current, manually'efiecting desired amplitudevariations in said current, making a control record of said amplitudevariations, repeating said audible reproductions of said current and theamplitude variations thereof under control of said control record, andsimultaneously rerecording said control record,said rerecorded controlrecord being adapted to embody any manual amplitude variations madeduring the audible repetition of said signal current.

f WALLACEV. WOLFE.

